Biohydrogen from microalgae

Direct biohydrogen production from chitosan harvested microalgae biomass and an isolated yeast

“…In other studies, it was also necessary to add an extra substrate concentration such as glucose 10 times more than the used at the present study to reach a higher biohydrogen production of 2.6-2.8 mol mol -1 by mol of glucose equivalent. Additionally, it has been reported that pure strains from Clostridium, Enterobacter and Thermotoga gives high hydrogen yields [2]. However, it is difficult to maintain a pure strain when it is looking for reducing cost to work with mixed cultures or residual streams.…”

“…There is also has been reported the process of pre-concentration by gravity sedimentation or flotation however additional steps are required [5]. The harvesting process lets to recover microalgae biomass of a high diluted culture (0.5-5 g/L), which can have small cells sizes (<30 μm), by mechanisms such as suspension stability and by the negative surface charge [1][2][3].…”

“…For, the harvesting process there are available chemical compounds, which are divided in three categories such as inorganic principally iron and aluminum salts like ferric chloride, aluminum sulfate and ferric sulfate, which are commonly used for the water treatment industry. The second category, inorganic polymers such as polyacrylamide and polyelectrolyte and the third category the organic compounds, which are polymers flocculants [8,9] and naturally modifier polymers such as guar gum, Moringa oleifera seed flour and chitosan, this last one is a cationic polyelectrolyte derived by the deacetylation of chitin and whose characteristics are non-toxic, non-corrosive, biodegradable and don't produce sludge or metal salts hazardous for microalgae biomass uses such as animal feed or fertilizer [2,8,10]. Also, with the organic ones, are raised high flocculation efficiencies under low dosages conditions.…”

“…A promising organic compound to harvest microalgae is chitosan, which it has been demonstrated that is not toxic after harvesting microalgae biomass, making viable to reuse the supernatant and process biomass without any additional treatment to produce biofuels, being a potential opportunity to reduce cost [9]. However, it still remains with some disadvantages such as pH dependent, the solubility lack and for some microalgae species ineffective because of the low concentration reached and the undesired ions separation under high dosage, affecting the reuse of supernatant [2].…”